Reassessing perennial cover as a driver of duck nest survival in the Prairie Pothole Region

Abstract

Conservation plans designed to sustain North American duck populations prominently feature a key hypothesis stating that the amount of the landscape in perennial cover surrounding upland duck nests positively influences nest survival rates. Recent conflicting research testing this hypothesis creates ambiguity regarding which management actions to pursue and where to prioritize conservation delivery. We compared existing models and new formulations of existing models explaining spatiotemporal variation in nest survival using independent data documenting the fate of >20,000 duck nests within the Drift Prairie, Missouri Coteau, and Prairie Coteau physiographic regions of the United States Prairie Pothole Region during 2002–2018. Our results suggest an inconsistent relationship between perennial cover and survival of upland duck nests, which depended upon physiographic region and current and time‐lagged landscape and environmental conditions. The magnitude and direction of how perennial cover correlated with daily nest survival depended on its dominance as a landcover type. A positive relationship existed when perennial cover was a minor component of landcover in all physiographic regions (<30% of a 10.4‐km2 area) and, in the Drift Prairie and Prairie Coteau, when perennial cover was the dominant landcover type (>60%). A constant or negative relationship was predicted at locations of about 30–60% perennial cover. Additionally, environmental conditions (i.e., density of wetlands and estimated gross primary productivity in the previous year) moderated or enhanced the effect of perennial cover on nest survival, depending on physiographic region. Our finding of inconsistency in the relationship between perennial cover and nest survival contradicts the conservation premise that nest survival universally increases linearly when uplands are converted to perennial cover. Promoting policies and management actions designed to increase perennial cover can be expected to be situationally but not consistently associated with higher survival of upland duck nests.

Waterfowl distribution and productivity in the Prairie Pothole Region of Canada: tools for conservation planning

“…States PPR, which also demonstrated that the positive response of nest survival to perennial cover is reduced, and may decline, when perennial cover dominates a landscape (Pearse et al 2022). While the mechanism is unclear, this may reflect a shift in predation rate as predator community and habitat composition change from grasslands in the south to aspen parkland in the north , Sargeant et al 1993.…”

Wetland occupancy by duck broods in cropland‐dominated landscapes of the United States Prairie Pothole Region

“…Sovada et al (2000) observed a positive relationship between grassland patch size and duck nest success, primarily due to increased predator efficiencies and marginal nest success in small, isolated patches. Other researchers also reported increased nest survival with more grassland (Duebbert and Kantrud 1974, Greenwood et al 1995, Stephens et al 2005) though recently that relationship has been challenged by Pearse et al (2022).…”

“…We sought to characterize metrics for grassland and wetland availability surrounding surveyed wetlands to evaluate relationships between landscape composition and wetland occupancy by broods. Grasslands have been considered important determinants of duck nesting success in many studies (Greenwood et al 1995, Reynolds et al 2006, Pearse et al 2022). Bloom (2010) demonstrated female mallards selected areas with greater wetland densities to raise a brood, presumably because of reduced duckling survival with increased overland travel in areas with few wetlands (Rotella and Ratti 1992 b , Ball et al 1995), increased competition from conspecifics in low wetland density areas (Krapu et al 1997), or fewer available inundated wetlands as dry summer conditions progress.…”

“…nest success in small, isolated patches. Other researchers also reported increased nest survival with more grassland(Duebbert and Kantrud 1974, Greenwood et al 1995, Stephens et al 2005) though recently that relationship has been challenged byPearse et al (2022).…”

Climate and Land Use Driven Ecosystem Homogenization in the Prairie Pothole Region

“…In the absence of prairie buffers (surrounding wetlands), agricultural runoff into wetlands is associated with greater rates of sedimentation, increased nutrient loads, and pesticide impacts [50,[75][76][77], which in turn can alter the chemical and biotic composition of affected wetlands. The loss of surrounding grasslands also becomes a loss of habitat and inter-wetland connectivity for species that require grasslands in addition to ponded wetlands to complete their lifecycle, e.g., waterfowl, amphibians [78][79][80][81]. The cumulative effects of wetland loss and the conversion of prairie to cropland in the PPR have simplified the spatial distribution of wetland basins and the upland landscapes in which they are embedded, and reduced ponded-water variability in remaining wetlands.…”